Area infiltration of subcutaneous tissue with anesthetics or other fluids is well known, especially in the field of reconstructive surgery. Patients often remain conscious during this type of surgery, requiring the specific localized area to be anesthesized. Various needles of conventional design are presently available to infiltrate these areas with local anesthesia or other fluids. Some of the anesthetics and other fluids used in these procedures, such as lidocaine HCl, commonly available under the brand name Xylocane, or benzocaine, are highly toxic to the patient and can create serious problems if the medicine is injected into the bloodstream instead of the subcutaneous or fatty tissue. Therefore, with conventional needles, great care must be taken to assure that a blood vessel is not punctured and injected with a toxic substance.
A standard procedure has been developed by physicians to prevent the injection of toxic fluids into blood vessels during area infiltration of subcutaneous tissue. The needle is inserted into the tissue to the desired position. The needle is then retracted slightly and the syringe piston is displaced so as to create a partial vacuum within the syringe. If a blood vessel has been punctured, the syringe will fill with blood, providing a visual verification that a vessel has been punctured. If, upon retraction of the needle, the syringe does not fill with the blood, then it is apparent that a vessel has not been punctured and injection of the fluid may proceed. Slight retraction of the needle after insertion is required to assure that a vessel has not been punctured; otherwise, the aperture of the needle may be in contact with an interior vessel wall. The contact between the needle aperture and the inner wall can seal the needle aperture preventing blood from flowing through the needle into the syringe. This procedure is time-consuming for the physician and can result in increased pain for the patient since injection of an anesthetic, is precluded until the needle has been fully inserted and slightly retracted to check for the presence of blood in the syringe.
In addition to the extra time required and pain which a patient must undergo while an area is anesthetized in the conventional manner, the patient is also subjected to multiple skin punctures caused by the needle since the needle is normally inserted in a variety of places in order to infuse a relatively large area. Patients undergoing this type of treatment usually suffer from hematomas due to the large number of punctures made.